1. Field of the Invention
The present invention is directed toward the SF-25 antigen of colon adenocarcinoma cells, and to antibodies, and in particular, monoclonal antibodies, which are reactive against this antigen. The invention is further directed toward continuous hybridoma cell lines capable of secreting such monoclonal antibodies, and to methods of using these antibodies.
2. Background of the Invention
The ability to generate monoclonal antibodies has enabled the identification of tumor-associated antigens. Monoclonal antibodies of relevant specificities can be valuable reagents not only for immunodiagnosis and immunotherapy, but also in the study of tumor cells in general. Examples of various neoplasms to which monoclonal antibodies have been generated include leukemia (Seon et al., Proc. Natl. Acad. Sci., USA 80:845 (1983); Aota et al., Cancer Res. 43:1093 (1983); Royston et al., TransDlan. Proc. 13:761 (1981)); glioma (Bourdin et al., Canc. Res. 43:2796 (1983); Schnegg et al., Canc. Res. 41:1209 (1981)); melanoma (Dippold et al., Proc. Natl. Acad. Sci., USA 77:6114 (1980); Carrel et al., Canc. Res. 40:2523 (1980)); breast carcinoma (Colcher et al., Proc. Natl. Acad. Sci., USA 78:3199 (1981); Schlom et al., Proc. Natl. Acad. Sci., USA 77:6841 (1980)); lung carcinoma (Cuttitta et al., Proc. Natl. Acad. Sci., USA 78:4591 (1981)); cervical carcinoma (Handley et al., PCT Publication No. WO 83/04313 (1983)); bladder carcinoma (Masuko et al., J. Natl. Cancer Instit. 72:523 (1984); Messing et al., J. Urol. 132:167 (1984); Grossman, J. Urol. 130:610 (1983); Stramignoni et al., Intl. J. Cancer 31:543 (1983); Herlyn et al., Proc. Natl. Acad. Sci., USA 76:1438 (1979); Kasai et al., J. Surg. Res. 30:403-408 (1981)); and prostate carcinoma (Ware et al., Canc. Res. 42:1215 (1982); Starling et al., Canc. Res. 42:3714 (1982)). The detection and characterization of human tumor antigens using monoclonal antibodies has been reviewed by Lloyd, "Human Tumor Antigens: Detection and Characterization with Monoclonal Antibodies," In: Herberman, ed., Basic and Clinical Tumor Immunology I:159-214, Nijoff, Boston (1983). Lloyd's review includes a discussion of the use of monoclonal antibodies to detect colorectal cancer. Lloyd, supra, at 181-182.
Colon and rectal cancers accounts for approximately 20% of all deaths due to malignant disease in the United States. The cause of colorectal carcinoma, which affects men and women approximately equally, is not known. Despite advances in management of colorectal cancer, the death rate for this disease is the same today as it was 40 years ago. The most significant factor in the poor prognosis for colorectal carcinoma is delay in diagnosing the disease. Because symptoms of colorectal carcinoma are frequently vague and nonspecific in the early stages of the disease, detection is often delayed. As a result, the cancer is often so well established by the time a positive diagnosis is made that a cure is difficult or impossible. Thus, for example, patients whose tumor is confined to the bowel wall generally have an excellent chance for cure following surgical resection (five-year survival rate&gt;95%). Where the tumor has extended to the serosa and mesenteric fat, however, the five-year survival rate following resection declines to 80%. Lymph node metastases reduce the five-year survival rate to 40%, while distant metastases (e.g., liver, lung, bone, brain) reduce the five-year survival rate to zero.
Commonly used screening tests for colorectal carcinoma contribute to delayed detection of the disease. For example, the guaiac test, which detects occult blood in the stool, requires that a colonic malignancy be advanced to the bleeding stage before it can be detected. Moreover, this test suffers from low and variable sensitivity due to dye instability. Sigmoidoscopy requires that any colorectal carcinoma be visible, and diagnosis may be complicated by the presence of other lesions such as hemorrhoids, polyps, and proctitis. Colonoscopy has similar drawbacks.
The inadequacies of presently available screening methods may be one reason that many colorectal cancers are first diagnosed as a result of a complication of the original lesion. For example, a bowel wall may be perforated by the tumor, causing acute peritonitis. Obviously, in such a case, the cancer will be well advanced by the time a diagnosis is made.
Delayed detection, then, is a major factor contributing to an overall five-year survival rate of only approximately 50% for colorectal malignancies. The diagnosis and treatment of colorectal cancer is described in LaMont et al., "Disease of the Small and Large Intestine," In: Petersdorf et al., eds., Harrison's Principles of Internal Medicine10th Edition, McGraw Hill, Publisher, New York, pp. 1762-1765 (1983).
Colorectal carcinomas generally respond poorly to chemotherapy. Although palliation may be effected, chemotherapy has not been shown to prolong the lives of patients diagnosed as having colorectal cancer, especially when the disease is widely disseminated. DeVita, "Principles of Cancer Therapy," In: Harrison's Principles of Internal Medicine. supra at 783 and Table 125-7.
The potential specificity of monoclonal antibodies for antigenic determinants associated with human tumor cells has led researchers and clinicians to investigate monoclonal antibodies for diagnostic and therapeutic use in the management of colorectal cancer. The potential clinical usefulness of monoclonal antibodies includes the detection of human cancers by immunohistochemistry (Gatter et al., Semin. Oncol. IX:517-525 (1982); Herlyn et al., Proc. Natl. Acad. Sci., USA 76:1438-1442 (1979)), radioimaging (Neville et al., Hum. Pathol. 13:1076-1081 (1982)), and the use of monoclonal antibodies as therapeutic agents (Levy et al., Ann Rev. Med. 34:107-110 (1983)).
For example, Sakamoto et al. (European Patent Publication No. 0 119 556 A2), disclose the use of a panel of monoclonal antibodies raised in mice immunized with human gastrointestinal tumors to diagnose the presence of colon cancer. These monoclonal antibodies recognize antigenic determinants present on normal as well as cancerous gastrointestinal cells. Although it is stated that these monoclonal antibodies can be used to treat gastrointestinal tumors, the significant cross-reactivity of these monoclonal antibodies with normal tissue minimizes their therapeutic utility. The antigens recognized by this panel of monoclonal antibodies were either glycoproteins or glycolipids having molecular weights of 25 Kd, 29 Kd, 52 Kd, or 95 Kd. Four of the 12 monoclonal antibodies were of class IgM. The IgM monoclonal antibody showing the best reactivity with colon carcinoma cells (12/17) cross-reacted with pancreatic cancer, breast cancer, bovarian cancer, and lung cancer cells. Moreover, it cross-reacted with normal adult tissue from lung, liver, gallbladder, esophagus, colon, pancreas, ureter, breast, prostate, sweat glands, and secretions.
Lindholm et al., Intl. Arch. Allergy Appl. Immunol. 71:178 (1983), immunized mice with a colorectal adenocarcinoma cell line for liver metastasis membranes from a patient having colon adenocarcinoma to produce monoclonal antibodies. Three monoclonal antibodies of class IgM were identified that reacted with colorectal adenocarcinoma cell lines, extracts of pooled adenocarcinomas and individual gastrointestinal tumors, but not with other cell types. The antigen complex was identified as a monosialoganglioside, but the antigen was not characterized further.
Koprowski et al., U.S. Pat. No. 4,349,528, describe the production of a monoclonal antibody specific for commercial carcinoembryonic antigen (CEA) having a molecular weight of about 180 Kd. The monoclonal antibody did not bind to antigens of colorectal carcinoma cells having molecular weights other than 180 Kd. r Sakamoto et al., Fed. Proc. 44(3):792 (Abstract 2222) (1985), describe antigens from human colon carcinoma which reacted with monoclonal antibodies obtained by immunization with cultured human colon and pancreas carcinomas, or with lysates of colon cancer cells. Two of the antigens K-314 (gp17O) and V-215 (gp14O) were detected only on colon and a few lung cancer cell lines. Neither the class of monoclonal antibodies involved nor the individual specificities of these monoclonal antibodies with respect to the antigens is disclosed.
Herlyn et al., Proc. Natl. Acad. Sci., USA 76(3):1438 (1979), describe the detection of a colorectal carcinoma-specific antigen using monoclonal antibodies (1083-17 and 1116-56) detected 8/9 human colorectal carcinomas. No data are presented characterizing the physical or chemical characteristics of the antigen involved. Both monoclonal antibodies were of class IgM.
Magnani et al., Science 212:55 (1981), describe the partial characterization of an antigen present on colon carcinoma cells which reacts with a monoclonal antibody. The molecular weight of the antigen, which was not purified to homogeneity, was not determined, although it was concluded that the antigen was a monosialoganglioside based upon its chemical reactivity and susceptibility to certain enzymes. The antigen was also found in human meconium, a rich source of normal fetal glycolipids.
Steplewski et al., Canc. Res. 41:2723 (1981), describe the release of monoclonal antibody-defined antigens by human colorectal carcinoma and melanoma cells. Some of the antigens detected were released into the tissue culture, while others could not be detected in tissue culture supernatants. It is stated that a monosialoganglioside antigen was released by tumor cells, but not by normal colon tissue, and that this antigen was not found in the serum of normal individuals. However, the antigen is not characterized further. Three other monoclonal antibodies (NS-3a-22, NS-10, and NS-33a) reacted with a glycolipid antigen released by most colorectal carcinoma cells. Two of these (NS-33a and NS-10) were of isotype IgM.
Herlyn et al., Intl. J. Cancer 27:769 (1981), studied the complement-dependent cytotoxicity of four hybridoma cell lines (NS-10, NS-33a, NS-38a, and NS-38c), which produced colon carcinoma-specific antibodies of isotype IgM. These monoclonal antibodies showed complement-dependent cytotoxicity against colon carcinoma cells.
Chang et al., Hybridoma 1:37 (1981), describe the detection of a monoclonal antibody-defined colorectal carcinoma antigen using a solid-phase binding inhibition radioimmunoassay. Two of the monoclonal antibodies were reported to be specific for antigen present on colorectal carcinoma. This antigen could be extracted from colon carcinoma cells using 3M KCl and was a glycolipid.
The diagnostic use of monoclonal antibodies in colorectal carcinoma is reviewed by Lloyd, suora, and by Davis et al., In: Prasad et al., eds., Novel Approaches to Cancer Chemotherapy, Academic Press, New York (1984) (see, e.g., Table III at page 43, setting forth tumor-associated antigens of gastrointestinal and colorectal tumors (among others) identified by various investigators.
As the above discussion demonstrates, despite longstanding scientific interest in the development of monoclonal antibodies to human colorectal carcinoma antigens, a need has continued to exist for a monoclonal antibody that shows a high degree of specificity for colorectal carcinoma. Such a monoclonal antibody should show no significant cross-reactivity with either normal human tissues or other malignant cell types.